PostgreSQL 10 High Performance - Third Edition

I/O scheduler elevator

One of the more controversial tunable Linux performance features, in that there are no universally accepted guidelines available, is that of the I/O scheduler choice. The name elevator is used due to how they sort incoming requests. Consider a real elevator, currently at the first floor. Perhaps the first person in requests the ninth floor, then the next person the third. The elevator will not visit the floors in the order requested; it will visit the third floor first, then continue to the ninth. The scheduler elevator does read and write sorting to optimize in a similar fashion.

You can set the default elevator scheduler at kernel boot time. Here's an example from a RedHat Linux system, changing the default elevator ...